Negotiations between the English and Dutch in 1664 aimed at preventing war figure prominently in Gregory's engaging sixth historical featuring intelligencer Thomas Chaloner (after 2010's A Murder on London Bridge). Among those in St. Margaret's Church observing Chaloner's wedding to Hannah Cotton, lady-in-waiting to the queen, is a shabbily dressed uninvited guest, Philip Alden, a Royalist spy during the Commonwealth. As the bride and groom proceed up the aisle after the ceremony, a woman sitting next to Alden screams; someone has fatally stabbed Alden in the back. Soon after, Willem Hense, the Dutch brother of Chaloner's late first wife, is found floating in the Thames. Multiple plot lines—involving a blackmailer, sabotage aimed at the Dutch delegation, and a shadowy figure who may be behind all the mayhem—make close reading a must. As usual, Gregory does a fine job integrating fact and fiction. (July)